I´ve trying to synthesise ZnO thin films using Sol Gel via Spin Coating, with a solution of Zn acetate dihydrate (0.59 M), Ethanol and a MEA:ZnAc molar ratio of 1.2. Generally the solution comes transparent after stirring for 30 min at 80 C. but after half an hour the solution turns turbid and starts to form visible aggregates.
The relative humidity oscillates between 35% and 55%
Dear Victor Perez Pimienta, possibly ethanol has been lost at such temperature and time stirring. Water already existing in your formulation. My Regards
Victor Perez Pimienta
Sol / gel method first you get a sol (poorly soluble nanoparticles of zinc hydroxide) by hydrolysis reaction at the cation and anion
Zn2+ + 2H-O-H = Zn(OH)2 + 2H+
CH3COO- + H-O-H = CH3COOH + OH-
The greater the dilution of the solution with water, the greater the degree of hydrolysis.
Over time, the dispersion ages, the zinc hydroxide dehydrates and a zinc oxide gel forms.
See a similar synthesis of nanoparticles.
Article Synthesis of Nanoparticles of Basic Copper (II) Acetate in M...
Victor Perez Pimienta Almost certainly you have slow hydrolysis to Zn(OH)2.
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